Brew Methods #4 – Cold Brew (Immersion Method)
You’ve seen those elaborate glass and wood towers in some cafes right? Those are used to make cold brew, but more specifically, cold drip. The way it works, is you let cold water drip through a bed of ground coffee. The variables in play are the brew ratio (coffee to water ratio), and the flow rate (which is usually controlled by a valve). The process takes a few hours and produces something that is full flavoured, but doesn’t have any bitterness. Hot water extracts everything from ground coffee, including caffeine, and other bitter plant alkali. Cold water doesn’t and hence the distinct lack of bitterness.
There’s another way to achieve a similar result. That’s to use an immersion brewing method. The ground coffee basically sits submerged in water for the duration of the brewing time (often in the fridge, but it can be done at room temperature as well). It’s a lot simpler, can have bigger yields per batch, and also doesn’t require an expensive structure to get the job done.
I’ll be going through the immersion method. Here’s what you need for equipment:
2x food grade buckets (size is up to you, but is the main determinant of batch size)
A colander that will fit inside the buckets
A tea towel (reserve it for use only with cold brew)
Wooden spoon
Kitchen scale
Kettle
Water filter jug (always used filtered water when making coffee)
A screw top container to store the brew in the fridge
Coffee-wise, you will need a similar grind size to plunger. You can grind coarser or finer to tune the flavours if you wish. I use 5 litre buckets, with the strainer from a kilo of ricotta (easily bought from the supermarket). As for brew ratio, I typically do a 10:1 water to coffee. My normal batch size is about 3 litres, so that’ll be 3 litres of water to 300 grams of coffee.
The boring method is to simply put the coffee in the bucket, add water, stir, put in fridge, and then strain. The method isn’t tricky, but there are some things you can do to take it to the next level.
Place bucket onto scale, and measure out ground coffee to your preferred ratio
Boil up about 500 millilitres of filtered water, let sit 5 minutes
Add hot water to coffee, just enough to saturate the grounds (usually 1/6 of the total water volume)
Stir the grounds to ensure complete saturation and let sit for 30 seconds
Add the rest of the volume of cold water, and give another brief stir
Place in the fridge, and allow to brew for 18-24 hours. Make sure that you cover the bucket to keep smelly fridge items from tainting the brew
After the requisite brew time, remove the brew from the fridge in order to strain
Place the colander into the second bucket, and line the colander with the tea towel (this is your coffee filter, make sure the tea towel doesn’t have too much aromatics from laundry powder – rinse several times, wring out, and let air dry)
Slowly pour the brew into the tea towel/colander combo. Don’t pour too fast, because it can splash everywhere
As you reach the end of pouring out the brew, be careful as the grounds will collapse, causing another messy situation. Try to get as much of the brew out as you can
Allow the brew to completely filter out. Gather up the sides, and squeeze out the remaining brew. Dispose of grounds in the green bin
Rinse off the tea towel and allow to air dry. For cleaning, just soak the tea towel in hot water with napisan, rinse completely and air dry
Pour brew into container and store for up to 2 weeks. The brew and be enjoyed cold or heated in the microwave, and can diluted to suit your taste
